The airline said it had grounded around 1,000 flights Monday, with hundreds more delayed, after a loss of power in Atlanta affected its system-wide operations. The airline usually operates around 6,000 flights a day.
The company said reducing its Tuesday morning schedule will allow it to "reset" the airline.
"Following the power loss, some critical systems and network equipment didn't switch over to Delta's backup systems. Delta's investigation into the causes is ongoing," the company said.
Delta said the power outage took place at 2:30am Eastern Time, causing it to ground flights at 5am.
Local power company Georgia Power said on Twitter: "#Delta experienced an equipment failure overnight causing their outage. We are working closely w/ Delta as they make repairs."
#Delta experienced an equipment failure overnight causing their outage. We are working closely w/ Delta as they make repairs.
-- Georgia Power (@GeorgiaPower) August 8, 2016
"We were able to bring our systems back on line and resume flights within a few hours yesterday but we are still operating in recovery mode," said Dave Holtz, Delta's SVP of operations and customer center.
"We are sorry for what many of our customers have experienced over the past 24 hours, including those who remain at airports and continue waiting for their flights. We are doing everything we can to return our operation to normal reliability, but we do expect additional delays and cancellations."
Following the outage, the airline grounded flights awaiting departure although those already en route operated normally.
The airline is offering a travel waiver for passengers due to fly on August 9, plus compensation to customers significantly affected by delays or cancellations; customers are being provided with hotel rooms if a cancellation leads to an overnight stay. As operations recover, unaccompanied minors who haven't begun travel won't be accepted until after August 10, but can be rebooked without a fee.